Influence of Mineral Montmorillonite on Soil Suction Modeling Parameters of Natural Expansive Clays

Expansive soils exhibit swell/shrink behavior with fluctuating moisture conditions arising from seasonal changes. Pore-water interactions occurring at the micro scale level of the soil specimen during swelling are mainly caused due to adsorptive forces and diffuse double layer charges on the clay particles. This chemical behavior is mainly attributed due to the presence of clay minerals such as Montmorillonite and is hypothesized that there is a strong correlation between soil water–suction relationship and percent clay mineral Montmorillonite. In the present research, an attempt is made to establish this relationship by studying natural compacted expansive clays and studying their respective soil water characteristic curve (SWCC). Four high plasticity expansive clays are selected and studied for mineralogy, expansive behavior and unsaturated properties. Soil water characteristic curves of these soils are determined from pressure cell technique and filter paper method. SWCC data was fitted against Van Genuchten and Fredlund and Xing models and the obtained model parameters are compared with the percent clay mineral in the soil. Test results from this research reemphasized the fact that that clayey soils with higher percentages of Montmorillonite content exhibited higher swelling behavior. Test results also showed that there is inconsistency with pore distribution SWCC modeling parameters with varying mineral content. Addressing the relationship between the percent Montmorillonite in a soil to SWCC modeling parameters is the main outcome.